U.S. Pat. No. 8,092,129 to Wiley, et al., which is incorporated by reference herein in its entirety, discloses a variety of bonding washer configurations for creating an electrical bond between metal pieces that are to be mechanically fastened together, such as photovoltaic panels and their supporting aluminum rails. Many of these bonding washers and their commercial counterparts and variants have oppositely directed teeth designed to penetrate the anodic coatings of the metal pieces when clamped together. Some have features that retain them in position on one metal piece to facilitate assembly with another metal piece. In some embodiments the teeth are positioned to engage the metal pieces near their fastener holes, while in others the teeth are positioned to engage the metal pieces near their outer edges. Typically, these bonding washers are designed to be compatible with specific metal piece profiles and/or widths.